The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Design and development of automatic transmissions for motor vehicles is ongoing. Given the multiple goals of improved performance, improved fuel economy and reduced cost, nearly every aspect of automatic transmissions has been scrutinized, evaluated and re-evaluated.
One of the areas of focus is the torque converter and the torque converter clutch. In order to achieve disconnection between the engine and transmission when the vehicle is in gear and stopped and allow the engine to idle, in order to provide a smooth launch, and in order to increase low speed torque, a torque converter is disposed between the output of the engine and the input of the transmission. The hydrodynamic fluid coupling and torque multiplication provided thereby achieves and satisfies all the foregoing requirements.
Unfortunately, it does so in a somewhat expensive and inefficient manner. The frictional losses in a torque converter contribute to the reduced efficiency and fuel economy of an automatic transmission relative to a manual transmission.
One approach to improving the efficiency of a torque converter involves the addition of a torque converter clutch or “TCC,” a clutch in mechanical parallel with the torque converter which is engaged when the transmission reaches an upper gear (lower numerical ratio), thereby locking out the torque converter and avoiding or minimizing its inherent fluid and frictional losses. While the addition of a torque converter clutch has a significant impact on efficiency and fuel economy, it also increases the cost and complexity of the torque converter, the transmission and the powertrain. Hence, there is a desire to develop mechanical assemblies which, while providing the benefits of lock up torque converters, do so with reduced complexity and cost.
The present invention represents a further improvement relating to automatic transmissions and torque converter assemblies.